For those who don’t know, public transport in Christchurch is in a bad way. And I spend an unhealthy amount of time thinking about how to fix it. Pre-earthquake Christchurch enjoyed a successful bus system, with reasonably high public transport patronage which was growing every year. Then in 2011 the earthquakes happened and that all changed. The city centre emptied out. Activity dispersed. Patronage plummeted. Various changes have been made to try and fix it. But we’re now seven years on and public transport patronage in Christchurch is still floundering.
To get my fix, I decided to do some analysis on accessibility to the city centre by public transport. Most cities in the world do something like this, but I’ve never seen it done for Christchurch. This website here (www.mapnificent.net) has some nice interactive maps showing how much of the city can get to the CBD by public transport within various times. But Christchurch hasn’t been mapped. ATAP included something along similar lines for Auckland, although far more comprehensively. This paper here (https://marroninstitute.nyu.edu/uploads/content/Cities_as_Labor_Markets.pdf) explains why connecting residents to jobs is a good thing, and this one https://smartgrowthamerica.org/resources/measuring-access-to-opportunity/) goes into more detail about how best to try and measure this.
I took inspiration from these sources, but because I was doing it in my spare time I had to simplify things. I downloaded the open source software QGIS and freely available bus and street information.
I mapped out how much of the city is within a half hour bus and walk trip of the city centre (using the central city bus change as the centre point). A few disclaimers:
- I only used the high-frequency bus network
- I based speeds on the timetabled speeds during the AM peak period (arriving at the bus exchange at 8:30am on a weekday).
- I included a wait time of half the peak period headway (which is 15 minutes on most routes).
- Likewise I included a transfer wait time of half the peak period headway.
- I used a commute time of 30 minutes as the cut-off, as this seems to be commonly used internationally.
- Population data was taken from the 2013 census (this showed 344,000 people living in Christchurch, excluding satellite towns like Rolleston and Rangiora).
Firstly, the map below shows in green how much of the city could get to the CBD in half an hour if there were no buses at all, just walking. The fuzzy grey dots denote population density, the black lines are the high frequency bus routes.
Roughly 23,000 residents (7% of the population) live within this green blob and can walk to the CBD in half an hour.
Secondly, the map below shows in blue how much of the city could get to the CBD in half an hour with the current bus network.
A much larger 106,000 residents (31% of the population) live within this blue blob and can get to the CBD in half an hour by walking and bussing.
Thirdly, I thought I’d see what happened if we put in more bus lanes and bus priority. This increases the bus speeds in congested parts of the network. To simulate this I just increased the routes with the lowest bus speeds (15-20km/h), up to a fairly modest 20km/h average speed (based on timetabled speeds of buses on bus lanes in Wellington and Auckland).
If we did this a slightly higher 119,000 houses (34% of the population) could get to the CBD in half an hour. It has less impact than I was expecting, mainly because the average speed of 20km/h I used is only slightly faster than what the buses are going at currently.
Fourthly, I thought I’d see what happened if we doubled frequencies on all routes. This halves the waiting and transfer times.
If we did this, an additional 41,000 houses could get to the CBD in half an hour, bringing the total to 147,000 (43%).
Fifthly, the map below shows the results if we both put in more bus lanes/priority and doubled frequencies.
If we both put in better bus priority and doubled frequencies across the core bus network, then 163,000 (47% of the population) could get to the CBD in half an hour.
Two things stand out to me about these results:
- Contrary to what you often hear in the media, a lot of Christchurch is actually not too badly serviced by public transport, with about a third of the population currently able to get into the CBD in half an hour or less, including walking and waiting time. But this is offset by large swathes of Christchurch that are poorly serviced by public transport.
- With investment solely in our existing bus network we could get around 163,000 people within a half hour commute of the CBD by bus (a 50% increase on the current 106,000). This would have huge benefits in terms of maximising the city’s labour pool, and would massively boost the usefulness of the bus network in Christchurch for all sorts of non-commuting trips too.
To me it’s encouraging that investing in increasing frequencies and speeds of buses would make a significant different to the number of people able to catch the bus into Christchurch CBD in a reasonable timeframe.
Next post – how would trains change this picture?
Feel free to comment below – I’d be interested to hear anyone’s thoughts on what you would do to fix the Christchurch bus system if you had the chance?